Obj-C内存管理初级

#import <Foundation/Foundation.h>
#import "Person.h"
#import "Student.h"
#define RELEASE_SAFE(_point) [_point release];_point = nil;
int main(int argc, const char * argv[]) {

    //自动释放池
    //是一种栈结构，每当遇到一个autorelease就将他入栈
    //当出了自动释放池，将栈中所有对象引用计数减一
    @autoreleasepool {
     
        //p1的引用计数为1
        Person *p1 = [[Person alloc] init];
        NSLog(@"%ld",[p1 retainCount]);
        
        //retain
        Person *p2 = [p1 retain];
        NSLog(@"%ld",[p2 retainCount]);
//        Person *p3 = [p1 copy];
//        NSLog(@"%ld",[p3 retainCount]);
        [p1 release];
        NSLog(@"%ld",[p1 retainCount]);
        [p2 release];
        //retainCount不记录0
        NSLog(@"%ld",[p2 retainCount]);

        //引用计数为1
        Person *p1 = [[Person alloc] init];
        //引用计数为2
        Person *p2 = [p1 retain];
        //引用计数为1
        [p1 release];
        //安全释放
        p1 = nil;
        //引用计数为0
        //这个release没有效果
        [p1 release];
        //利用带参宏便捷，安全地释放空间
        RELEASE_SAFE(p2);
 
  
        Person *p1 = [[Person alloc] init];
        Person *p2 = [[Person alloc] init];
        p1.name = @"庞麦龙";
        p1.books = @[@"十万个冷笑话",@"尸兄"];
        
//        [p1 retain];
        
        //autorelease不会立即对引用计数减一
        //离开自动释放池后，引用计数减一
        [p1 autorelease];
        [p2 autorelease];
//        NSLog(@"%ld",[p1 retainCount]);
         
    }
    //凡是一次alloc，配套一次release或者autorelease
    //凡是一次retain，配套一次release或者autorelease
    //凡是一次copy，配套一次release或者autorelease
    //谁污染谁治理
 
    Person *p1 = [[Person alloc] init];
    Person *p2 = [p1 copy];
    
    p1.name = @"如花";
    p2.name = @"铁柱";
   
    NSLog(@"%@",p2.name);
    RELEASE_SAFE(p2);
    RELEASE_SAFE(p1);
    [p1 copy];
  
    Student *s1 = [[Student alloc] init];
    s1.name =@"xuesheng";
    s1.age = 1;
    Person *s2 = [s1 copy];
    s2.name = @"taibao";
    NSLog(@"%@",s1.name);
    RELEASE_SAFE(s2);
    RELEASE_SAFE(s1);
　　 /*
     *不建议使用实例对象的方式建立AutoreleasePool
     */
    NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init];
    //池区,无作用域问题，autorelease的对象需要使用安全释放
    Person *p1 = [[Person alloc] init];
    [p1 autorelease];
    [pool release];
    pool = nil;
    p1 = nil;
    return 0;

}

#import <Foundation/Foundation.h>

@interface Person : NSObject<NSCopying>

@property(nonatomic,copy)NSString *name;
@property(nonatomic,retain)NSArray *books;


@end

#import "Person.h"

@implementation Person

//销毁对象
- (void)dealloc
{
    //当对象引用计数为0时，自动调用dealloc方法
    NSLog(@"啊，I‘m over!");
    //在一个对象销毁之前，清楚自己实例变量指向的内存
    [_name release];
    [_books release];
    
    //最后销毁从父类继承的东西
    [super dealloc];
}
- (id)copyWithZone:(NSZone *)zone{
    //浅拷贝
//    return [self retain];
    
    //深拷贝
    Person *p = [[Person allocWithZone:zone] init];
    p.name = [NSString stringWithFormat:@"%@",self.name];
    p.books = [NSArray arrayWithArray:self.books];
    return p;
}
@end

#import <Foundation/Foundation.h>

@interface Student : NSObject<NSCopying>
@property(nonatomic,copy)NSString *name;
@property(nonatomic,assign)NSInteger age;

@end

#import "Student.h"

@implementation Student
- (void)dealloc{
    [_name release];
    [super dealloc];
}

- (id)copyWithZone:(NSZone *)zone{
    Student *s = [[Student allocWithZone:zone] init];
    s.name = [NSString stringWithFormat:@"%@",_name];
    s.age = _age;
    return s;
}
@end